Bidentate

Bidentate

A bidentate ligand is a type of ligand in coordination chemistry that can form two bonds with a central metal atom or ion. The term "bidentate" comes from the Latin words "bi," meaning two, and "dentate," meaning toothed, indicating that the ligand has two "teeth" or donor atoms that can attach to a metal center.

Structure and Bonding

Bidentate ligands have two donor atoms, which are typically atoms with lone pairs of electrons such as nitrogen, oxygen, or sulfur. These donor atoms are capable of forming coordinate covalent bonds with a metal ion. The two donor atoms are usually part of a single molecule, and they are positioned in such a way that they can simultaneously bind to the same metal center, forming a chelate ring.

Chelate Effect

The ability of bidentate ligands to form stable chelate rings with metal ions is known as the chelate effect. This effect is a result of the increased stability of the metal-ligand complex due to the formation of a ring structure, which reduces the entropy loss upon binding compared to monodentate ligands.

Examples of Bidentate Ligands

Some common examples of bidentate ligands include:

• Ethylenediamine (en): A simple bidentate ligand with the formula NH₂CH₂CH₂NH₂, where both nitrogen atoms can coordinate to a metal center.
• Oxalate (C₂O₄²⁻): An anion derived from oxalic acid, where both oxygen atoms can coordinate to a metal ion.
• 1,10-Phenanthroline: An aromatic bidentate ligand with nitrogen donor atoms that can form stable complexes with transition metals.

Applications

Bidentate ligands are widely used in various fields, including:

• Catalysis: Many catalysts in industrial and laboratory processes involve metal complexes with bidentate ligands, which can enhance the reactivity and selectivity of the catalyst.
• Medicine: Bidentate ligands are used in the design of metal-based drugs, such as platinum-based anticancer agents, where the ligand helps to stabilize the metal center and modulate its biological activity.
• Analytical Chemistry: Bidentate ligands are used in the formation of metal complexes for spectroscopic and chromatographic analysis.

Also see

• Ligand
• Coordination chemistry
• Chelate
• Monodentate
• Polydentate

Coordination Chemistry
Main concepts
Coordination complex Ligand Coordination number Chelation Crystal field theory Ligand field theory Isomerism in coordination complexes
Types of ligands
Monodentate ligand Bidentate ligand Polydentate ligand Ambidentate ligand Bridging ligand
Applications
Bioinorganic chemistry Catalysis Medicinal chemistry Materials science
Notable complexes
Hemoglobin Chlorophyll Cisplatin Ferrocene
Related topics
Inorganic chemistry Organometallic chemistry Transition metal Metal complex